1. Field of the Invention
The present invention relates to a robot system and a robot controller.
2. Description of the Related Art
In the prior art, in a device having a shelf on which an article can be located, the shelf can be moved while the article is located thereon, so as to convey the article to a predetermined place. In such a device, the shelf may be configured to be moved while the orientation of the shelf may be always kept in the horizontal state, in order to prevent the article on the shelf from falling from the shelf (e.g., see JP S55-161718 A, JP 2017-001759 A, and JP 2003-044135 A).
On the other hand, it is a well-known technique to control a robot so that the robot can follow the movement of a workpiece on a conveyor and can perform a predetermined operation of the workpiece (e.g., see JP 2002-192486 A).
In the prior art, when a robot should be controlled so that the robot can follow a workpiece on a conveyor configured to move (or rotate) along a circular trajectory, the position and orientation of the robot at each time point is calculated based on a rotating coordinate system defined at a rotation center, and the robot is controlled based on the calculated position and orientation. However, when the robot must follow a shelf of the conveyor, the orientation of which is always kept constant (e.g., in the horizontal state) during the rotation of the conveyor, the shelf in the horizontal state is rotated relative to the robot, since the position and orientation of the robot are controlled based on the rotating coordinate system. Therefore, when the motion of the robot (e.g., aligning articles on the shelf) should be taught while taking the orientation of robot into consideration, the orientation of the robot must be taught while taking the action of the shelf into consideration. Such teaching may be burdensome and difficult.